Sealing device for electrified particle accelerator

ABSTRACT

A sealing device for an electrified particle accelerator consisting of a flexible ring-shaped membrane surrounding the output of the tube and joining this output to the wall of the pressurized chamber in which the tube is arranged vertically. The membrane having a U-shaped meridian cross section with vertical branches. One figure.

[ Aug. 21, 1973 United States Patent [191 Dedieu References Cited UNITED STATES PATENTS SEALING DEVICE FOR ELECTRIFIED PARTICLE ACCELERATOR Runoe...... 250/49.5 A

[73] Assignee:

Telecommunications Cit-Alcatel, P im ry Examiner-Roy Lake Paris, France Assistant Examiner-James B. Mullins A!torneySughrue, Rothwell Mion, Zinn & Macpeak [22] Filed: Mar. 12, 1971 [5 7] ABSTRACT A sealing device for an electrified particle accelerator consisting of a flexible ring-shaped membrane surrounding the output of the tube and joining this output App]. No.: 123,521

[30] Foreign Application Priority Data Mar. l3, l970 France 7009179 to the wall of the pressurized chamber in which the [52] US. Cl. 313/63 tube is arranged vertically, The membrane having a U- [51] Ill. shaped meridian cross section with vertical branches [58] Field of 313/63; 250/495 A, O figur 5 Claims, 1 Drawing Figure Patented Aug. 21, 1973 INVEHTOQ PAUL .DED/EU guakfim ,RM M

SEALING DEVICE FOR ELECTRIFIED PARTICLE ACCELERATOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to linear accelerators of electrified particles, such as protons and electrons. While linear accelerators generally pertain to electrons and for the sake of simplification, will be described in thhis environment, it should be understood that the invention applies as well to other charged accelerators, such as proton or deuton.

2. Description of the Prior Art An electron accelerator generally utilizes a tube devoid of all gas in which the acceleration of the charged particles is performed. The charged particles are then employed for their desired effect in an appropriate zone. It is often necessary to adjust the direction and position of an electron beam as it arrives in this utilization zone. In one practical form, an electron accelerator constitutes as essential component in an electron microscope. The beam of accelerated electrons penetrates the electron optics assembly, which constitutes the microscope and accordingly must be capable of adjustment, both with respect to direction and position of the electron beam. This adjustment poses particularly tough problems in the case of a microscope having an extremely high acceleration voltage, for example 1,000,000 volts. It is clear that the adjustment in this environment must be capable of being performed with extremely great precision because of the high performance expected of the apparatus.

Because of the high voltages involved, the accelerator tube is enclosed in a chamber which contains a high gas pressure with good dielectric characteristics, such as sulphur hexaflouride SF Becasue this chamber has considerable dimensions and weight, it is important that it remain fixed during the operations involved in adjustment of the accelerator tube. To permit this, a highly flexible sealing device is therefore necessary between the output of the accelerator tube and this chamber. The necessity of this sealing device is particularly important in the cases where large dimensions and the heavy weight of the accelerator tube are likely to entail major elastic deformations in the structures, which makes it necessary to be able to compensate for these deformations and to have a broad adjutment range. Further, a large degree of flexibility of the sealing Joint is often necessary, not only to permit precise regulation in terms of position and direction, but also to prevent the transmission of vibrations to the accelerator tube. The prior art has attempted to utilize numerous ealing devices to provide a flexible and tight connection. Some of these prior art devices involve elastomer membranes that utilized the elastic expansion of the membranes to provide the flexiblity of the sealing joint. These elastic membranes often are designed with undulations or corrugations to increase their flexiblity. Generally these elastomer membranes are not used to guarantee the tightness of the chamber, which is designed to suppPrt major pressure differentials.

In some electron accelerator tubes, the sealing connecting device for the vacuum chamber is made up of thin sheet of the inoxidable steel that is corrugated in the form of a bellows, that is, certain zones of this connecting sealing device presents a meridian cross section in the form ofa U. The branches of the U being perpendicular to the axis of the accelerator tube. The particular rigidity of such a sealing seat, however, permits the transmissions of vibrations.

SUMMARY OF THE INVENTION The present invention provides a sealing device between a linear electron accelerator or other charged particle accelerator and a chamber containing this accelerator. The sealing device of the present invention permits a large deformation range along with a great flexiblity, while still being capable of supporting great pressure differences without transmitting the vibrations.

The present invention provides a sealing device that prevents the transmission of vibrations between a first end of an electrified particle accelerator tube and the edges of an opening made in the wall ef a pressurized chamber containing this tube. This is accomplished by providing a flexible ring-shaped membrane attached by its inside edge to the accelerator tube and by its outside edge to the chamber wall. Generally the chamber wall is considered thick, with respect to the position and orientation of the accelerator tube. The sealing device is characterized by providing the flexible membrane having a surface divided Into an internal peripheral zone attached to the accelerator tube, a median zone, and an external peripheral zone attached to the chamber wall. These three zones being concentric with the internal and external peripheral zones being included between the median zone and respectively the inside and outside edges of the membrane. The median zone provides over its entire length a meridian cross sectional U- shaped configuration with the arms of the median zone being essentially straight and parallel to the axis of the accelerator tube. The membrane is made up of an elastomer material that can, during the longitudinal movement of the accelerator tube, permit the curved portion of the median zone to adjust to accommodate the movement. The median zone is squeezed between an external guide attached to the chamber wall and an internal guide attached to the accelerator tube, each of the guides presenting a guide surface in contact with one of the branches surrounding the median zone.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a vertical sectional view of the flexible sealing joint of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the figure of the drawing, an electron microscope having an acceleration voltage on the order of one million volts, is disclosed. The accelerator tube of the microscope is placed inside a tight chamber within which there prevails a pressure of approximately 5 bars of SF The accelerator tube is connected with an appropriate connecting tube, which in turn, communicates with the optical portion of the microscope. The accelerator tube has a shape that is of a cylinder fonn, with the vertical axis. In the figure, the wall 2 of the accelerator tube, the wall 4 of the connecting tube, and the wall 6 of the chamber can be seen.

Due to the accuracy requirements, the weight problem, and the pressurized condition, the present seal must guarantee both a tight and flexible connection between the wall 2 of the accelerator tube and the wall 6 of the chamber. This sealing connection must be capable of containing both the pressure of the SF exerted from the inside of the chamber and under certain conditions, the atmospheric pressure from the outside when the chamber is emptied of gas.

The sealing connection provides an elastomer membrane 8, which may be reinforced with polyamide wires. The cross section of this membrane, in its median zone, has the shape of a U whose vertical branches curve back toward the outside of the chamber at the upper end until they become eventually horizontal. The internal peripheral zone of the sealing joint 8, that is to say, the zone situated to the right in the figure, is squeezed against the base of the accelerator tube 2 by a clamp 12, supported on this base by screws, such as 14. Likewise, the external peripheral zone of sealing joint 8, that is to say, the zone situated to the left in the figure, is secured in a tight manner against the reinforced border 16 of the chamber wall 6, by a clamp 18 applied against this border by screws, such as 20. The border 16 is equipped with a prolongation 22, vertically penetrating to the interior of the median zone of the membrane 8 and forming a supporting surface for the purpose of limiting the deformation of the sealing joint when vacuum exists inside the chamber wall 6.

The base 10, border 16, clamps l2 and 18 and prolongation 22 are all appropriately rounded in those areas where they may come into contact with the sealing joint 8. The clamps 12 and 18 are Further prolonged downward by collars 24 and 26 which are coaxial to the accelerator tube 2, and which are suitable in forming guides for the sealing joint 8 during the vertical movements of the accelerator tube 2. For example, when the accelerator tube 2 is raised with respect to the chamber wall 6, the sealing Joint 8 is moved in contact upon the vertical outside face of the collar 24. If, on the other hand, the accelerator tube 2 is lowered with respect to the chamber wall 6, the sealing joint contacts the inside face of the collar 26.

For the purpose of replacing the sealing joint 8, the clamps l2 and 18 can be removed. Further, the connecting tube 4, can be slid vertically because of a guiding joint arranged in its lower portion which is not shown here, to permit the removal of the old sealing joint 8 and the insertion of a new sealing joint. The base 10 and the border 16 contain along their peripheral surface grooves for alignment or locating the sealing joint 8.

During the normal operation, the accelerator tube 2 is supported upon the connection tube 4 and tightness is guaranteed by a toric joint 28. Since the connection tube 4 must be able to slide and cannot easily support the weight of the accelerator tube 2, it is necessary to provide it with means of support. These means of support are not shown in the figure, but they are removable so as to permit the lateral displacement and replacement of sealing joint 8. During this replacement of the sealing joint 8, it is obviously necessary to support the accelerator tube 2, since the latter is no longer supported bytube 4. For this purpose, a certain number of screw jacks, such as 30, are incorporated in the border 16 of the chamber wall 6, and the accelerator tube is equipped with support angle irons, such as 32. Before the replacement of the sealing joint 8 and after the removal of clamp 18, the accelerator tube 2 is slightly raised by means of the angle iron 32 with the help of the jacks 30. During the sealing joint 8 replacement operation, the accelerator tube 2 is then supported by the chamber wall 6. During this replacement, the interior of the chamber has been evacuated of SP and the tank is in communication with the atmosphere.

Although the above description discloses the preferred embodiment of the present invention, it is obvious that artisians in the art could make various modifications within the scope of the present invention and accordingly, the aforementioned should be interpreted in accordance with the following claims;

What is claimed is:

I. In combination with a charged particle accelerator tube and a pressurized chamber, a sealing joint permitting relative movement of the tube and chamber without transmitting vibrations comprising a flexible ringshaped membrane attached respectively on its inside and outside edges to the accelerator tube and chamber, the central portion of the membrane having a cross sectional U-shape, a first guiding securement means for fastening the edge of the membrane to the chamber and guiding the U-shaped portion during a relative adjustment of the accelerator tube and chamber and a second guiding securement means for fastening the edge of the membrane to the accelerator tube and guiding the U-shaped portion during a relative adjustment of the accelerator tube and chamber.

2. The combination of claim 1 further including an internal guiding means located within the chamber and positioned within the U-shaped portion to limit internal displacement of the U-shaped portion.

3. The combination of claim 1 where the alignment ridges are provided on the membrane.

4. The combination of claim 2 where jacks are provided on the chamber and supports are provided on the accelerator tube to permit the chamber to support the accelerator tube while the membrane is replaced.

5. The combination of claim 4 where alignment ridges are provided on the inside and outside peripheral area of the membrane. 

1. In combination with a charged particle accelerator tube and a pressurized chamber, a sealing joint permitting relative movement of the tube and chamber without transmitting vibrations comprising a flexible ring-shaped membrane attached respectively on its inside and outside edges to the accelerator tube and chamber, the central portion of the membrane having a cross sectional U-shape, a first guiding securement means fOr fastening the edge of the membrane to the chamber and guiding the U-shaped portion during a relative adjustment of the accelerator tube and chamber and a second guiding securement means for fastening the edge of the membrane to the accelerator tube and guiding the Ushaped portion during a relative adjustment of the accelerator tube and chamber.
 2. The combination of claim 1 further including an internal guiding means located within the chamber and positioned within the U-shaped portion to limit internal displacement of the U-shaped portion.
 3. The combination of claim 1 where the alignment ridges are provided on the membrane.
 4. The combination of claim 2 where jacks are provided on the chamber and supports are provided on the accelerator tube to permit the chamber to support the accelerator tube while the membrane is replaced.
 5. The combination of claim 4 where alignment ridges are provided on the inside and outside peripheral area of the membrane. 